Commutator undercutting tools



c. R. KINNAMAN 2,898,814 coMMUTAToR UNDERCUTTING TOoLs Filed Oct. 27, 1958 United States Patent() COMMUTATOR UNDERCU'ITING TOOLS Chalmer Ross Knnaman, Lafayette, Ind. Application October 27, 1958, Serial No. 769,948

- I1 claim. (c1. 9o-38) This inventionrelates to new and useful improvements in commutator undercutting tools, and the principal object of the invention is tofacilitate quick, easy and accurate undercutting of insulation between the segments of commutators of large industrial generators and motors, such as for example those used in diesel' locomotives, although the use of the invention is by no means limited ,to this vparticular environment.

As -is well known, the commutator insulation is required to be maintained below the periphery of the commutator segments and since the diameter of the commutator continually decreases, either -as a result of wear by brushes contacting the same or by periodic turning of the commutator in a lathe, it is necessary at intervals to undercut the insulation to its proper level below the periphery of the segments. In large generators and motors the commutator is of a formidable size, perhaps 3 feet in diameter and 8 inches wide, containing literally hundreds of segments and insulation layers therebetween. As such, the conventional procedure cf manually undercutting the commutator by scraping the nsulation with Va hand tool or cutter is -a very time-consuming and dicult task which often fails to be carried out with proper accuracy.

The present invention eliminates the above outlined disadvantages by the provision of a-power driven tool which may be conveniently manipulated, even in poorly accessible locations, for quickly and accurately undercutting the commutator in a fraction of the time previously required for performing the task by hand.

Other advantages of the invention reside in its simlcity of construction, in its adaptability to economical manufacture, and in its adaptability for use on commutators of different sizes and types.

With the foregoing vmore important objects and features in view and such other objects and features as may become apparent as this specification proceeds, the invention will be understood from the following description taken in conjunction with the accompanying drawings, wherein like characters of reference are used to designate like parts, and wherein:

Figure 1 is a longitudinal sectional view of the invention taken in a vertical plane;

Figure 2 is a side elevational View thereof;

Figure 3 is a horizontal sectional view, taken substantially in the plane of the line 3 3 in Figure 1; and

Figure 4 is a vertical sectional view, taken substantially in the plane of the line 4-4 in Figure 1.

Referring now to the accompanying drawings in detail, the commutator undercutting tool in accordance with the invention is designated generally by the reference numeral 10 and embodies in its construction a horizontally elongated housing 11 including a plateshaped upper portion 11a and a tapered lower Aportion 11b provided at the bottom thereof with a longitudinally extending slot 12.

An elongated blade holder 13 is reciprocable in the blade, or the like.

j 2,898,814 Patented Aug. 11., 17959 housing 11 and has a tapered lower portion provided with a longitudinally extending groove 14 which is aligned with the slot 12 and is adapted to receive therein a suitable cutting blade 15, such as rfor example a hacksaw The cutting edge portion of the blade 15 projects outwardly throughl the slot 12 beyond the bottom edges 11c of the housing at opposite sides of the slot, the extent of projection of the blade corre- .sponding to the depth of undercutting, so that when the tool is placed in use by applying it to a commutator as exemplified in Figure 4, the housing portions 11c may abut the commutator segments 16 and limit the extent to which the blade may penetrateA and undercut the insulation 17 between the segments.l

The blade15 is removably secured in the groove 14 of the holder 13 by a plurality of screws 18 with which thev holder is equipped, the housing 11 being provided at one side thereof with slots 19 whereby access to the screws may be-had regardless of the particular position at which the reciprocable-holder may be vdisposed in the housing,

The means for reciprocating the holder comprise a vertical drive Shaft 20 having its lower end portion rotatably journalled in an aperture 21 formed in the housby nuts 24 on threaded upper portions 25a: of a pair of studs 25 which also have threaded lower portions 25b secured' in threaded apertures formed in the housing portion 11a, as is clearly shown in Figure 1. The upper end portion of the shaft 20 projects from the bushing 22 and is adapted to be connected to any suitable source of power, such as for example, the chuck of a portable electric drill (not illustrated).

A pair of studs 26 are screw-threaded into the blade holder 13 and project upwardly therefrom through slots 27 formed in the housing portion 11a, the studs 26 having enlarged heads 26a at their upper ends in abutment with a tie strap 28 through which the studs pass. A cam 29 is suitably secured to the shaft 20 between the bushing 22 and the housing portion 11a, and operatively engages a pair of cam follower rollers 30 which are rotatably mounted on the respective studs 26 between the housing portion 11a and the strap 28.

As is best shown in Figure 3, the studs 26 and the rollers 30 thereon are disposed at longitudinally opposite sides of the shaft 20 and cam 29, so as to translate rotary motion of the shaft into a reciprocating movewith the holder, it is formed with la central opening` 31 to provide clearance for the bushing 22. Suitable washers 32 are provided on the shaft 20 and the studs 26 between the cam 29 and rollers 30, respectively, and the housing portion 11a, as is best shown in Figure 1.

An elongated dome-shaped cover 33 is fsecured by suitable screws 34 to the top plate 23 and encloses the cam and follower mechanism so as to protect the same from dirt, moisture, et cetera` The cover may be easily removed upon removing the screws 34, it being noted that the cover is provided with openings 35 to accommodate the nuts 24, so that the nuts need not be removed during removal of the cover.

A substantially U-shaped yoke 36 is secured by suitable screws 37 to one end portion of the housing 11 and is provided with a longitudinally projectingk screwthreaded stud 38 having a nut 39 thereon. 'Ihis nut may be 4adjusted in a suitable position on the stud so as to abut any suitable stationary structure 40 in the vicinity` in place by the nut-'39, thus eliminating the needjto steady the-housingrbyhand-when fthe device is in use.

Whilein the foregoingthere has been shown-and described therpreferred embodiment ofthe invention, vari- Y out modifications may become apparent to those skilled inthe art to which the invention relates. Accordingly, it is not desired `to limit the invention to this disclosure, and various modifications may be resorted to, such `as may lie within thefspirit -and scope of the'A appended claim. Y p Y Whatisclaimedvas new is: 4 n

In a commutator undercutting tool, 'the combination of an elongated housingincluding a plate-shapedupper portion and provided inrits bottom portion with a longiv tudinally extending slot, an elongated blade holder disposed wholly within'and reciprocable in vsaidhousing and formed in its. bottom portion with a longitudinally extending groove aligned with said slot, an elongated cutting blade removably mounted inthe groove of said holder and having a longitudinal cutting edge portion projecting outwardly through the slot of said housing, a

Y top plate secured to said upper portion of 'the housing in upwardly spaced relation therefrom, a drive shaft rotatably journalled in said upper housing portion and said top plate, a cam rotatable with said drive shaft, and cam follower means carried by said blade holder and operatively engaging said cam, the bottom portion of said holder being ush with the bottom of the housing and bottom portions of said housing at opposite sides of said blade constituting Work abutting means for limiting the extent of penetration of the blade into the work, saidcam follower means comprising a pair of studs secured to said holder and projecting upwardly through slots formed in the upper portion of the housing at longitudinally opposite sides of said drive shaft, a reciprocable tie strap carried by said studs in upwardly spaced relation from said upper portion of the housing, said tie strap being formed with an opening movably receiving said drive shaft, and a pair of vrollers rotatably mounted on the respective studs between the upper portion of the housing andsaid tie strap,vsaid rollers engaging said cam.

References Cited in the rile of this patent Bianchini Mar. 18, 1958 

